Growing onions from seed not that hard

Sunday

Feb 28, 2010 at 3:15 AM

Winter is muddling along, as am I. Winter is starting to feel tedious, especially since recently the cross-country skiing has been dicey at best.

So I shall turn to gardening again soon, and start some onions, shallots and/or leeks by seed. These are plants that need a good head start — you really should start them between now and mid-March for best results.

You may wonder why I bother growing onions. After all, onions are cheap to buy and onions are onions, right? Wrong. Onions vary as much in flavor as tomatoes, or at least raw in a salad they do.

I still have onions in my pantry from last summer, and I get pleasure every time I chop one up to sauté it. It connects me with my garden, and is a little taste of summer.

My yellow 'Copra' onions are storing well in my cool, dark pantry, and should last until June — 9 months after harvest.

There are two ways to start onions: indoors now by seed, or outdoors in the spring by planting sets (little bulbs). Most gardeners don't want to mother seedlings for 2-3 months indoors, so they plant sets. Onion sets are, actually, tiny onions that were grown last year to be used this year. But they were mistreated early in life: they were crowded so badly that they never developed into edible onions, remaining little runty things.

I believe that starting onions from seeds and setting out plants instead of sets gives bigger, more vigorous onions. You can buy little plants in bundles of 50, come spring, in some garden centers or from catalog companies (www.johnnyseeds.com or 877-564-6697).

Onion seeds are tiny and hard to plant individually. I don't start them in plastic 6-packs, but rather those plastic containers that are like the 6-packs but have no divisions. I plant onion seeds in a 50-50 mix of commercial potting soil and high-grade compost.

I sprinkle seeds on the surface, water them, and then cover them with just a thin layer of potting soil that I put in a sieve or colander and shake over the surface. That gives a fine covering, but not so much as to bury the seeds deeply. Sometimes I sprinkle agricultural vermiculite instead of potting soil on the surface, as it holds water well and is very fine.

Like most vegetables, onions need lots of light when grown indoors. I set up 4-foot, two-tube fluorescent fixtures over them. I hang the fixtures from a jack chain about 6 inches above the tips of the plants, and raise the lights as they grow.

In order to get strong, stout onion plants, I give them a haircut when they are about 6 inches tall, taking off a couple of inches. Then, a few weeks later, I repeat the process. It's a good idea to water them with a dilute fish and seaweed fertilizer once a week.

Onions grow best in soil that has been made loose by adding lots of compost. Full-sized onions need to be spaced 3-4 inches apart, but you can plant closer than that and thin out the small ones early in the summer, allowing the rest to reach full size. Onions need to be kept weeded, but their roots are shallow and can be injured with weeding tools. A layer of leaf mulch minimizes the need to weed, and keeps the soil evenly moist, which onions need.

The development of an onion bulb is dependent on day length. Southern parts of the country need different onions than northern parts, where summer days are very long. If you buy plants or seeds locally you should be all right, or if you read your seeds catalogs carefully. There are a few day-neutral onions that will grow anywhere. Your onions are mature and ready to pick when their tops flop over.

The pungency of an onion depends on how much sulfur an onion picks up from the soil. Sweet onions like the Vidalia or the Walla-Walla will not be so sweet if grown in New England, where the soil has more sulfur than in the South or the far West. Not only that, the onion known as the Vidalia in the grocery store (called Granex in catalogs) is a short-day onion designed to grow in winter down South, and will not form a big bulb above the Mason-Dixon Line.

Shallots do not form big bulbs the way onions do, but their flavor is prized by serious cooks. You can plant them closer together than full-sized onions. If you plant scallions from sets, each will produce about 6 scallions; if starting from plants, you will get just one.

One 6-inch container of leek seedlings started indoors by seed will easily give me the 50 leeks I use each year. At planting time I tease the plants apart and plant them 4-6 inches apart in a furrow about 6 inches deep. The soil should be well amended with compost, and a little organic fertilizer.

As they grow, I fill in the furrow — this gives a bigger white portion of the leek at harvest time. I store leeks for winter by chopping them and freezing in zipper bags, as they don't store long in my root cellar or fridge — they tend to get slimy.

Light frost is not a problem for onion family plants, so I try to get mine outside and in the ground in late April or early May. So think about starting some onion-family seedlings soon. They are easy to maintain, and a pleasure to see growing indoors at this time of year.

Henry Homeyer is the author of three gardening books. He can be reached at henry.homeyer@comcast.net or P.O. box 364, Cornish Flat, NH 03746.

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